四種鰻 (日本鰻、鱸鰻、呂宋鰻、太平洋雙色鰻) 期玻璃鰻在臺灣與菲律賓呂宋島的地理分布與種類組成的季節性變化

Abstract

鰻魚為東亞國家臺灣、日本、韓國和中國大陸的重要養殖魚種，目前養殖業所需的鰻苗完全依賴漁民在河口的捕撈。然而，其資源量從 1970-1980 年代以後急遽地下降。在西北太平洋地區，臺灣與菲律賓呂宋島為數種鰻鱺屬幼苗重要的產區，為了維護與管理鰻魚資源及養殖產業，有必要瞭解鰻魚在臺灣與菲律賓呂宋島的地理分布和種類組成的季節性變化。 根據 DNA 的分子檢測發現臺灣與菲律賓呂宋島的鰻魚有四種，分別為日本鰻 (Anguilla japonica)、鱸鰻 (A. marmorata)、呂宋鰻 (A. luzonensis，又名黃氏鰻 A. huangi) 以及太平洋雙色鰻 (A. bicolor pacifica)。日本鰻與鱸鰻已有許多研究探討其生活史，但是呂宋鰻和太平洋雙色鰻的生活史相關研究仍然很少。本研究主要目的為調查上述四種種類的鰻苗在臺灣和菲律賓呂宋島北部的地理分布與種類組成的季節性變化。結果發現在呂宋島北部與臺灣，鱸鰻為全年出現的主要鰻種；在呂宋島北部，呂宋鰻為僅次於鱸鰻的優勢鰻種，主要出現於下半年，7-9月為高峰。相對於呂宋島北部，臺灣的呂宋鰻數量很少。同樣地，太平洋雙色鰻的相對豐度在臺灣與呂宋島北部均是較少的，主要出現在9-3月。此外，日本鰻集中在臺灣冬季出現，且其出現季節有明顯的地理傾斜現象。四種鰻苗在臺灣和菲律賓呂宋島北部的地理分布與種類組成的季節性變化之差異，可能與鰻苗之生殖季節以及上溯時的溫度偏好有關。

Eel is an important aquaculture species in Taiwan, Japan, Korea and China of East Asia, and the eel fry of aquaculture demand must completely rely on capture in the estuaries from fishermen. However, the glass eel resource has been declining rapidly from 1970-1980. In the Western North Pacific, Taiwan and northern Luzon Island of the Philippines are important producing regions for larvae of several Anguilla species. To maintain and manage eel aquaculture industry, the research on geographic distribution and seasonal species composition of glass eel is needed. According to the DNA molecular technique, four species of freshwater eel were identified in Taiwan and Luzon Island, namely Anguilla japonica, A. marmorata, A. luzonensis (syn. of A. huangi), and A. bicolor pacifica. Several studies have revealed the life history of A. japonica and A. marmorata, but the research about life history for A. luzonensis and A. bicolor pacifica are still rare. The study investigates geographical distribution and seasonal species composition of these four species of glass eel in Taiwan and northern Luzon Island of the Philippines. The results revealed that A. marmorata was the dominant species, occurring year round in Taiwan and northern Luzon Island. While sub-dominant species in northern Luzon Island was A. luzonensis, and presented in the second half of the year, with peak from July to September. Comparing with northern Luzon Island, the amount of A. luzonensis was fewer in Taiwan. Furthermore, the relative abundance (%) of A. bicolor pacifica was rare in Taiwan and northern Luzon Island, and appeared mainly between September and March. However, A. japonica was occurred in Taiwan in winter only, and the distinct geographic tilt was observed. The results revealed that the geographic distribution and seasonal composition of glass eels of four eel species were different, and this difference may be related to reproduction seasons and recruiting temperature preferences of the glass eel.